1. Field of the Invention
The present invention relates to a method and apparatus for setting a rotation speed of a drive motor or an internal combustion engine of any work machine that is operated at a constant engine or motor rotation speed while working. Especially the method relates to a self-propelled agricultural harvesting machine, such as a chopper-harvester, combine or harvester-thresher.
2. Prior Art
Work machines usually have an internal combustion engine, which drives the individual control or working elements and also can be used as the source of motive power for machine travel. The motors used are designed so that their power fits the required work necessary in the work process. The power provided in work machines, such as baggers, cranes or harvesting machines, is very much larger than necessary for machine travel. During the work process the motors are operated with a rotation speed, which guarantees optimum utilization of the drive power. The rotation speed is usually set so that it is constant. If it is necessary for the work process that the work machine be moved continuously at different travel speeds, the machines are equipped with a travel drive, which may be adjusted independently of the motor speed. The known travel drive is formed as a hydraulic pump/motor unit or as a Variator unit. The travel speed change is obtained by changing the fluid supply rate to the hydraulic motor and/or by changing the fluid volume drawn by the hydraulic motor. A transmission can be connected to the respective drive elements for increasing efficiency. This transmission can be shifted by an adjusting lever or also automatically in a known manner and frequently serves also for travel direction reversal of the work machine, in connection with a Variator travel drive.
The rotation speed of the internal combustion engine is controlled by variation of the amount of fuel injected. The adjustment can take place by a mechanical adjusting lever, electromotorized adjusting spindle, electropneumatically, electrohydraulically or also more recently by means of an electronically controlled fuel injection. In work machines the adjustment of the motor rotation speed is performed in steps or stages and in order to avoid working with incorrect motor rotation speed. Often only two stages are available so that the motor rotation speed can only be the idle speed or the maximum rotation speed necessary for the work process. For transport or road travel two travel speed ranges are needed for conveying travel or road travel, namely travel with motor idle speed or with the working motor speed. When the motor idle speed is used in conveying or road travel, the power performance of the motor in certain cases is insufficient and the motor can be killed or stall. Usually the conveying travel or road travel is performed with maximum motor rotation speed or with working motor rotation speed. This has the disadvantage that the motor or engine of the work machines produces unused drive power during conveying travel or road travel, which leads to unnecessary consumption of fuel and also produces excessive noise in the surrounding environment.
A method of reducing fuel consumption in self-propelled work machines during conveying is known from DD 200 234, in which the fuel consumption of the drive engine is reduced during transport or conveying by using an automatic constant motor speed lowered from the nominal motor rotation speed. The transport gear stage is designed so that the maximum permitted travel speed can be achieved with a reduced engine rotation speed. The vehicle operator sets the motor speed that has been lowered by a predetermined amount prior to the conveying or transport and engages the transport gear stage. A locking device prevents unintended engagement of the transport gear stage at the motor nominal speed. In an additional embodiment of the method, the adjusting of the shift lever is demanded or requested prior to setting the transport gear stage and on engagement of the transport gear stage the motor rotation speed is automatically lowered to the reduced motor rotation speed, at which the motor provides the maximum drive efficiency for conveying or transport.
The fuel consumption is reduced by the proposed method, but the motor rotation speed is optimally reduced only for drive performance during transport. The work machine still burns fuel unnecessarily and produces unnecessary noise at idle or with reduced drive performance requirements.
It is an object of the present invention to provide a method and apparatus for setting the rotation speed of a drive motor of a work machine of the above-described kind, in which the fuel consumption and noise generation during both transport and road travel are adjusted to optimize work machine performance.
According to the invention this object is attained by a method for setting the rotation speed of the engine in the work machine, in which the set rotation speed of the drive motor depends automatically on the set vehicle travel speed during transport travel or road travel.
By the method according to the invention the fuel consumption and noise generation are both reduced to a considerable extent during transport and road travel. The operator of the work machine, for example, has a switch available in the dashboard for setting the motor rotation speed. When the work machine has finished its work in one location and is required to travel to another location by means of its travel drive, the operator can selected the type of setting for the motor rotation speed according to the invention by means of the switch. The motor rotation speed setting then occurs automatically by setting the vehicle travel speed. These can occur by means of a foot pedal, an adjusting lever, a travel speed lever or also by an electronic determination of the pressure on the travel speed lever.
In the simplest embodiment of the invention the motor rotation speed switches from a higher motor rotation speed to the idle speed of the drive motor, when the vehicle is in the idle condition. This reduces the fuel consumption, for example, at an entrance or at a traffic light and also reduces the noise generation expected at the entrance or light. When the operator activates the drive of the work machine, for example, by operation of the drive pedal, the motor rotation speed is automatically increased from the idle speed to the higher rotation speed.
It is especially advantageous to set the motor rotation speed according to the position of a travel speed lever in a work machine. For example, the fluid feed rate of a hydraulic pump is set by a Bowden cable or by a electrohydraulic adjusting device. When the machine operator moves the travel speed lever into its neutral position during transport or road travel, a switch detects this motion and the motor rotation speed is automatically lowered. The lowering of the rotation speed does not necessarily continue until the idle speed is reached so that a higher motor rotation speed is available during subsequent starting of the work machine.
In work machines, in which the travel speed setting is uncoupled, for example by an electronically controlled adjusting pump, from the drive elements, it is also possible to carry out a changed setting of the vehicle speed either by a change of the motor rotation speed and/or by a change in the fluid feed rate to the hydraulic pump. It is also possible to react in one predetermined speed range by changing the motor rotation speed and in another or in a subsequent vehicle speed range by changing the fluid feed rate. Furthermore the relationship between the fluid feed rate and the motor rotation speed can be adjusted to the performance requirements of the travel drive so that an optimum fuel consumption with a minimum noise generation always takes place. For measurement of the required power performance with a hydrostatic travel drive, the rotation speed set in the drive motor and the feed rate to the adjusting pump or the draw volume of the adjusting motor can be determined with the help of the pressure in the hydraulic system. With an increased drive power demand the rotation speed is set to a higher value and at the same time the feed rate to the drive pump is reduced or the draw volume of the drive motor is increased. This occurs automatically in predetermined stages until the travel speed of the work machine is optimized. During a reduction of the drive power required for the travel drive, the method proceeds in the reverse manner from that described above in connection with the drive power increase.
In an additional embodiment of the invention the rotation speed of the drive motor is set according to the travel speed lever setting the travel speed of the work machine. The advantage of this process is that the work machine behaves for the operator according to the changes of the set travel speed. The machine then reacts like a motor vehicle. Furthermore the method according to the invention can compensate for nonlinearities between the travel speed lever positioning and the control of the travel drive, by a suitably programmed characteristic curve for the motor rotation speed.
Self-powered agricultural harvesting machines are usually equipped with a transmission or gear unit. Because of the transmission the hydrostatic drive unit or Variator can be economical constructed. The maximum achievable travel speed of the work machine is determined also by the selected travel speed range. A work machine has several travel speed ranges, which correspond to the required speeds in working operation and also for transport and road travel. The travel speed ranges for working and for transport and road travel differ from each other by means of different gear ratios in the transmission and other things, also by different preselected hydrostatic adjustments.
In an especially preferred embodiment of the invention the rotation speed of the drive motor is set according to the set travel speed of the work machine only in a predetermined travel speed range for transport and road travel. The selection of the method of setting the rotation speed is performed automatically and provides a further simplification for the machine operator. The selected travel speed range can be provided by known means, such as by a switch on the shift rod or on the transmission for the travel drive, which reads out the selected travel speed range or derives it from control signals for the hydrostatic devices (selected from different feed or draw volume ranges).
In another embodiment of the invention the rotation speed of the drive motor is set according to the set travel speed only during forward travel of the work machine. This is especially advantageous for work machines, which can be controlled for motion in different drive directions by means of a single travel speed lever. The operator of the work machine must observe the rear range, during rearward motion with the help of auxiliary devices, for example a mirror. This is preferably performed at reduced travel speed and at reduced motor rotation speed, so that an approaching person can still pay attention to an acoustic signal. The proposed method automatically lowers the motor speed, which would otherwise be lowered manually and thus an additional simplification is obtained for the operator. Furthermore less noise is produced for the surroundings.
The object of the invention also includes an additional process, in which the rotation speed of the drive motor is automatically set at the idle rotation speed when a change from working operation to transport or road travel is detected. Usually the work machine is prepared for transport to the next work field or for road travel after working operation. For this purpose safety devices, such as boundary lights and protective devices, are added manually to the devices of the work machine. So that the work machine does not consume unnecessary fuel and also does not generate excessive noise for the surroundings, the rotation speed of the drive motor is automatically reduced according to the described method. The change of the work machine, from work operation to transport or road travel can be detected from adjustments made by the machine operator in the work machine or from parameters of the work machine. Furthermore this process provides the advantage of an output adjustment for additional motor rotation speed control for transport or road operation differing from that during working operation.
An additional object of the present invention is an additional process in which the rotation speed of the drive motor is automatically adjusted to the idle rotation speed when a change from the transport or road travel to the working operation is detected. In this process fuel is saved and unnecessary noise is eliminated during the time required for setting the work machine up for working operation. When the work machine is brought, for example at a higher motor rotation speed, into a field, usually the work machine is halted and the protective devices removed and it is adjusted to perform the work process. During this time it is unnecessary to operate the drive motor with a higher rotation speed. This adjustment takes place automatically according to the described process.
The object of the invention is also obtained by an apparatus for performing the above-described method according to the invention. The apparatus includes means for setting the rotation speed of the drive motor according to means which determine the set travel speed of the work machine or which detect when the work machine is performing work or engaged in transport or road travel. Many adjustments of the work machine can be performed by electronically controlled devices. The setting of the travel speed can be performed in various ways and preferably takes place by means of a travel speed lever. The displacement of the travel speed lever from a neutral position in the simplest case is read off by means of a switch. In additional embodiments of the invention the position of the drive speed lever for different displacements is determined over the adjustment range by means of switches or also by means of a potentiometer. The set travel speed is made available to the devices according to the invention by means of known electrical transmission means, such as a vehicle bus system. The apparatus moreover is connected with means that allow a change of the work machine from work operation to transport and road travel, and the reverse, to be detected. This can be a simple switch that is mounted on the fittings of the work vehicle and is operated as needed by the operator.
In an additional embodiment of the apparatus according to the invention the respective changes of the work machine between working operation and transport or road travel can be automatically detected by monitoring at least one position or a combination of positions of different control or working members. The apparatus is thus provided with means that transmit the positions of the control members. For example the apparatus reads the position of the gearshift lever. The control member positions may be correlated individually, or also in certain combinations with other control member positions, with respective usage states of the work machine. The positions of control members in a harvester-thresher include generally the positions of switches in the operating fittings, such as the position of the drive coupling, the position of the gear shift lever or the position of the corn tank extension. If, for example, the drive member, such as the thresher drum, is shut off, the corn tank extension is brought in and put in the travel position, then the harvester-thresher is made ready for road travel. The apparatus of the invention in a chopper-harvester can communicate, for example, the position of the discharge elbow or the transport position of the storage unit or the gear shift lever position. If the discharge elbow does not find itself in the transport position and the road travel configuration is not detected, the harvester-thresher is in its working state.
The fuel consumption and the noise generation is reduced by this apparatus by the automatic setting of advantageous motor rotation speeds according to the method of the invention.